Limits of usefulness of electrophysiological methods for estimating dendritic length in neurones.

The present report deals with methodological problems concerning the electrophysiological analysis of multipolar neurones. In a nerve cell in which the dendrites may be considered as being equivalent to a single cable, the electrotonic length of the equivalent cable may be determined by analyzing the potential response to a step of current injected into the soma (Rall, 1969). In the present model study it is shown that this kind of analysis is unsuitable for discriminating between neurones with different dendritic lengths in excess of about 1.5-2.0 length constants.